The Diseases Of Electrical Machinery

ELECTRICAL MACHINERY. 43 and suitable method of connecting up the starter is shown in Fig. 23. Any sparking is prevented by this arrangement. The starters are usually constructed with three terminals, which are usually distinguished by three letters such as in the sketch, as L (line), N (shunt), and A (armature). It is to be noticed that a thin lead must be taken from the terminal N to the free end of the shunt winding, and a thick lead from A to that pole of the machine which is not directly connected with the shunt winding. These connec- Fig. 24. Fig. 25. tions are shown in Fig. 24. There are, however, two common ways in which mistakes are made. The more usual case is represented in Fig. 25. Here the marks on the resistance have been used correctly. The terminal L is connected to a lead, the free end of the shunt is connected to N; and to the terminal A one pole, but the wrong pole, is connected. The connec- tion has been made namely to the pole which is con- nected to the shunt winding, and the return lead is taken from the free pole. If one now considers what